At an initial stage of this field, a climbing step constituted by a substantially U-shaped or bent metalic bar was used in such a manner that its free ends are embedded into concrete. In the great majority of cases, however, the step member is exposed to the wind, rains or toxic gases, whereby the step member undergoes corrosion. For the purpose of preventing this kind of corrosion, there has been proposed a U-shaped step which is disclosed in the specification of U.S. Pat. No. 2,064,803, the arrangement being such that its portion exposed from the concrete is coated with synthetic resin.
The device of U.S. Pat. No. 2,064,803 certainly exhibited effectiveness against the corrosion. However, where a plurality of climbing steps are installed on the wall surface of, for instance, a manhole by embedding their proximal portions therein, a person ascending or descending the steps must search for the tread portion of the individual steps with his feet, because such steps are difficult to recognize by eyesight especially when used in poorly lighted areas.
On the other hand, the specification of Japanese Utility Model Laid-Open No. 66746/1985 discloses another type of step wherein a disc-like small reflection plate is embedded in a bend or angular portion formed at the boundary between an arm member and a tread portion of a U-shaped step coated with the synthetic resin. The reflection plate of this type involves a plastic transparent plate whose underside surface is formed with prism-like rugged portions. Problems inherent in this disc-like small reflection plate, however, arise because the plate is difficult to see on account of its smallness, and the plate is apt to separate from the plastic coating member.
In the specification of Japanese Patent Laid-Open No. 82838/1979, there is disclosed a climbing step having such a structure in which "retroreflection tapes" are bonded with the aid of a bonding agent to grooves formed in the upper surface of the step. The "retroreflective tape" is thin, and adhesion thereof entirely depends on the bonding agent which is previously applied to its hidden surface. Consequently, when employing this kind of tape for the climbing step, the tape is likely to be damaged or peeled off. In addition, the step portion to which the tape is bonded needs to be smooth. The tape is adhered after construction of the step and hence its manufacture undesirably requires one extra process.